When MPNZ's load shedding percentage exceeds 75%, the bar on the graph should move into a red zone. It signals the USI transmission grid is approaching peak loading and as MPNZ's load shedding percentage approaches 100% there is a reasonable likelihood of new chargeable peak periods occurring.

When the end of the bar is red MPNZ is deploying its maximum load control capability (100%). The longer MPNZ load shedding remains at 100% the more likely new chargeable peak periods will occur on the USI grid. This forms a reasonable signal for consumers to manage their load and to continue doing so until the bar on graph moves down from 100% and ceases to be red at the end.

When the whole bar is white (0%) MPNZ is not controlling any load and the grid will be operating at normal load levels. This bar is updated every 5 minutes.

Electromagnetic Fields

Electric and magnetic fields are produced by any wiring or equipment carrying electric current. This includes overhead and underground power lines carrying electricity, wiring in buildings and electrical appliances.

There are ongoing studies around the world looking into the effects of electromagnetic fields on the body.

New Zealand has an inter-agency committee headed by the Group Manager at the National Radiation Laboratory that reports to Government on a six-monthly basis and includes reviews of notable studies in electromagnetic fields being carried out around the world.

In late 2004, MainPower engaged the National Radiation Laboratory to carry out electric and magnetic field recordings at an existing 33kV to 11kV substation and in the vicinity of an existing 66kV overhead power line.